Clinical trials of alcohol use disorders (AUD) treatments have contributed significantly to the advancement of knowledge regarding treatment processes and outcomes. Such studies have yielded a strong evidence base regarding the efficacy of several psychosocial alcohol treatments, to include brief interventions. Irrespective o the proliferation of clinical trials research, based on manual driven treatments specifying underlying mechanisms of behavior change (MOBC), little is known about how such evidence based treatments actually work. Similarly, studies investigating assessment reactivity effects have contributed substantially to our understanding of alcohol treatment research assessment protocols influencing clinical outcomes (e.g., alcohol use), although empirical studies examining underlying mechanisms of behavior change have not been conducted. Thus, the state of the science is such that we know little about how specific alcohol treatments or research assessment protocols influence behavior change. This lack of understanding regarding the mechanisms by which alcohol treatments and research assessment protocols influence behavior change prompted NIAAA to release (2013) a funding opportunity announcement (PAR-14-051), titled Mechanisms of Behavior Change in the Treatment of Alcohol Use Disorders (R01), that specifically requests applications that identify the mechanisms that underlie how assessment reactivity operates within alcohol treatment protocols (p. 4). This application is in direct response to this funding opportunity announcement and centers on an investigation of mechanisms of behavior change underlying alcohol treatment research assessment reactivity. Enhanced understanding of the mechanisms that underlie psychosocial alcohol treatments and assessment reactivity has direct relevance for the design of alcohol treatment clinical trials, the interpretation of data derived from such studies, and for behavior change and its maintenance, which is essential for successful interventions. The long-term goal of the proposed research is to enhance clinical research and practice via a more in-depth understanding of the mechanisms that influence behavior change, thereby increasing the power of alcohol interventions to facilitate reductions in alcohol use.